I run a supa5 race bike in the BHR club and I run 1mm clearance and have no problems revving to 7000rpm and the bike seems fine at lower revs . but in theory the tighter squish should reduce the chance of detonation but the higher compression ratio should increase the risk but as these engines are generally quite low compression this should not be a problem. generally high compression gives an increase in torque but tends to reduce power at the very top of the rev range and lower compression seems to give a flatter lower torque curve